tree:   https://github.com/multipath-tcp/mptcp_net-next.git export
head:   502db67b77b326a9be8f3bb3515a09b83a8a1fd4
commit: 91e9b96e7c81bb06efcbd05a454d61c735f8c519 [776/783] mptcp: open code mptcp variant for lock_sock
config: x86_64-rhel-8.3 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/multipath-tcp/mptcp_net-next/commit/91e9b96e7c81bb06efcbd05a454d61c735f8c519
        git remote add mptcp https://github.com/multipath-tcp/mptcp_net-next.git
        git fetch --no-tags mptcp export
        git checkout 91e9b96e7c81bb06efcbd05a454d61c735f8c519
        # save the attached .config to linux build tree
        make W=1 ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp(a)intel.com>

All warnings (new ones prefixed by >>):

>> net/core/sock.c:2489:6: warning: no previous prototype for '__lock_sock' [-Wmissing-prototypes]
    2489 | void __lock_sock(struct sock *sk)
         |      ^~~~~~~~~~~

vim +/__lock_sock +2489 net/core/sock.c

  2488	
> 2489	void __lock_sock(struct sock *sk)
  2490		__releases(&sk->sk_lock.slock)
  2491		__acquires(&sk->sk_lock.slock)
  2492	{
  2493		DEFINE_WAIT(wait);
  2494	
  2495		for (;;) {
  2496			prepare_to_wait_exclusive(&sk->sk_lock.wq, &wait,
  2497						TASK_UNINTERRUPTIBLE);
  2498			spin_unlock_bh(&sk->sk_lock.slock);
  2499			schedule();
  2500			spin_lock_bh(&sk->sk_lock.slock);
  2501			if (!sock_owned_by_user(sk))
  2502				break;
  2503		}
  2504		finish_wait(&sk->sk_lock.wq, &wait);
  2505	}
  2506	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org